Cooling of Entrained Parcels in a Large-Eddy Simulation
Cooling of Entrained Parcels in a Large-Eddy Simulation
复制标题
大涡模拟中夹带颗粒的冷却
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
D. Randall
中科院分区：
文献类型：
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作者：
T. Yamaguchi;D. Randall
通过分析一个拉格朗日粒子跟踪模式（LPTM）与一个大涡模拟模式相结合的结果，对由于长波辐射、蒸发和混合引起的云顶卷吸冷却率的相对重要性进行了评估。LPTM使用主机模型模拟的解析速度预测每个包裹随时间的轨迹。LPTM可以识别夹带包裹，这在观测研究中几乎是不可能做到的。使用水平网格间距为5 m，垂直网格间距为2.5 m，对夜间层积云进行了4 h的模拟。在模拟的最后一个小时开始时，超过4000万个包裹被放置在逆温层顶部附近，然后被跟踪。通过分析包裹的历史来识别夹带包裹。夹带发生在云洞中，云洞发生在下沉空气的干燥区域。进入混合层的卷吸是由浮力调节的，这需要包裹在倒置的容器中预冷。
AbstractThe relative importance, for cloud-top entrainment, of the cooling rates due to longwave radiation, evaporation, and mixing was assessed through analysis of the results produced by a Lagrangian parcel-tracking model (LPTM) incorporated into a large-eddy simulation model. The LPTM predicts each parcel’s trajectory over time, using the resolved velocity simulated by the host model. An LPTM makes it possible to identify entrained parcels; this is almost impossible to do in an observational study.A nocturnal stratocumulus cloud was simulated over 4h using a 5-m horizontal grid spacing and a 2.5-m vertical grid spacing. At the start of the last hour of the simulation, over 40 million parcels were placed near the top of the inversion layer and then tracked. Parcel histories were analyzed to identify entrained parcels.Entrainment occurs in cloud holes, which occur in dry regions of sinking air. Entrainment into the mixed layer is regulated by buoyancy, which requires parcels to be precooled in the invers...